Seminars Archive

Large-Format, High-Speed, X-ray pnCCDs Combined with Electron and Ion Imaging Spectrometers in a Multipurpose Chamber for Experiments at 4th Generation Light Sources.

Abstract
Fourth generation accelerator-based light sources, such as VUV and X-ray Free Electron Lasers(FEL), deliver ultra-brilliant (~1012-1013 photons per bunch) coherent radiation in femtosecond (~10 fs to 100 fs) pulses and, thus, require novel focal plane instrumentation in order to fully exploit their unique capabilities. As an additional challenge for detection devices, existing (FLASH, Hamburg)and future FELs (LCLS, Menlo Park; SCSS, Hyogo and XFEL, Hamburg) cover a broad range of photon energies from the EUV to the X-ray regime with significantly different bandwidths and pulse structures reaching up to MHz micro-bunch repetition rates. Moreover, hundreds up to trillions of fragment particles, ions, electrons or scattered photons can emerge when a single light flash impinges on matter with intensities up to 1022 W/cm2. In order to meet these challenges, the Max Planck Advanced Study Group (ASG) within the Center for Free Electron Science (CFEL) has designed the CFEL-ASG MultiPurpose (CAMP)chamber. It is equipped with specially developed photon and charged particle detection devices dedicated to cover large solid-angles. A variety of different targets are supported, such as atomic, (aligned) molecular and cluster jets, particle injectors for bio-samples or fixed target arrangements. CAMP houses 4! solid-angle ion and electron momentum imaging spectrometers (“reaction microscope‿, REMI, or “velocity map imaging‿, VMI) in a unique combination with novel, large-area, broadband (50 eV to 25 keV), high-dynamic-range, single-photon-counting and imaging X-ray detectors based on the pnCCDs. This instrumentation allows a new class of coherent diffraction experiments in which both electron and ion emission from the target may be simultaneously monitored. This permits the investigation of dynamic processes in this new regime of ultra-intense, high-energy radiation – matter interaction. After a brief introduction into the salient features of the CAMP chamber and the properties of the redesigned REMI/VMI spectrometers, the new 1024 x 1024 pixel format pnCCD imaging detector system will be described in detail. Results of tests of four smaller format (256 x 512) devices of identical performance, conducted at FLASH and BESSY, will be presented and the concept as well as the anticipated properties of the full, large-scale system will be elucidated. The data obtained at both radiation sources illustrate the unprecedented performance of the X-ray detectors, which have a voxel size of 75 x 75 x 450 μm3 and a typical read-out noise of 2.5 electrons (rms) at an operating temperature of -50C.